Microstructural and ferroelectric properties of rare earth (Ce, Pr, and Tb)-doped Na _0.5 Bi _4.5 Ti ₃ O ₁₅ thin films

Pure Na _0.5 Bi _4.5 Ti ₄ O ₁₅ and rare earth-doped Na _0.5 Bi ₄ RE _0.5 Ti ₄ O ₁₅ (RE = Ce, Pr, and Tb) thin films were prepared on Pt(1 1 1)/Ti/SiO ₂ /Si(1 0 0) substrates by using a chemical solution deposition method. X-ray diffraction and Raman scattering spectroscopy studies revealed that the thin films are crystallized in a single-phase Aurivillius structure with no additional phases. The rare earth-doped Na _0.5 Bi ₄ RE _0.5 Ti ₄ O ₁₅ thin films exhibited improved electrical and ferroelectric properties. Among the studied rare earth metal ions, the Tb ³⁺ ion leads to a remarkable improvement in the ferroelectric properties. The use of the Tb ³⁺ ion for doping resulted in a well-saturated ferroelectric hysteresis loop with a large remnant polarization (2P _r ) of 40 μC/cm ² and a low coercive electric field (2E _c ) of 176 kV/cm, measured at an applied electric field of 475 kV in the Na _0.5 Bi ₄ Tb _0.5 Ti ₄ O ₁₅ thin film. Furthermore, the leakage current density of the Na _0.5 Bi ₄ Tb _0.5 Ti ₄ O ₁₅ thin film was one order of magnitude lower than that of the Na _0.5 Bi _4.5 Ti ₄ O ₁₅ thin film.